This invention relates to the manufacture of glycerol, betaine, succinic and/or lactic acid, potassium sulfate, and L-pyroglutamic acid. More particularly the invention relates to the recovery of the above products as a result of the fermentation and distillation of raw materials into ethanol and stillage, from which a free flowing distiller's dry grain or solid fertilizer is produced.
The manufacture of each of the products named above by other processes has been known heretofore, and all have commercial uses. Ethanol is used as a beverage, a chemical, and a fuel derived from renewable resources, and is typically manufactured by fermentation and distillation processes starting from biological materials such as corn, wheat or other grain, sugar cane or beets, grapes or other fruit, potatoes, cassava, sweet sorghum, cheese whey or the like. Glycerol, while known to be produced in small quantities as a by-product of ethanol fermentation and distillation processes or yeast and yeast extract production, has been manufactured commercially only by processes which have soap as the primary product or which synthesize glycerol from petrochemical feed-stocks. Betaine is conventionally produced synthetically or by crystallization of the aqueous liquors of beet molasses. Succinic acid is conventionally synthesized from maleic or acetic acid or produced by means of a highly specific fermentation. Lactic acid is conventionally produced by fermentation with Lactobacillus delbrueckii, B. dextrolacticus, or similar microorganisms. Potassium sulfate is conventionally obtained by reacting sulfuric acid with potassium chloride. Potassium chloride usually occurs in nature as the mineral sylvine or sylvite.
Distiller's dry grain, characterized as with (DDGS) or without (DDG) solubles, is conventionally produced as a by-product of fermentation and distillation processes. As such the resulting DDG or DDGS is usually infused with sticky by-products such as glycerol so as to exhibit poor flowing qualities and be difficult to handle. If the substrate from which distillates are produced is a sugar cane or beet material, then the residue is typically used only as a liquid fertilizer, feed additive or treated as a waste.
The manufacture of ethanol is sufficiently well known and the interested reader is referred to the available literature for descriptions of the basic processes. The manufacture of glycerol is, by way of example, discussed in Hildebrandt U.S. Pat. No. 2,169,245;; Wallerstein U.S. Pat. No. 2,772,207, to which the interested reader is referred.
Some suggestion that glycerol might be recovered from stillage appears in a presentation by Burris entitled "Recovery of Chemicals Such as Glycerol, Dextrose, and Amino Acids from Dilute Broths" which was presented to the "International Conference on Fuel Alcohols and Chemical from Biomass" on Nov. 10-12, 1986 in Miami Beach, Fla. The process there disclosed includes a very precise sequence of operations including ultrafiltration (organic membranes with pore size of &lt;0.1 microns), pH adjustment, filtration, ion exclusion, ion exchange, and carbon treatment. This sequence of operations has not proven to provide a commercially feasible glycerol recovery process.
Betaine production is, by way of example, discussed in U.S. Pat. No. 4,359,430 to Heikkila et al; Japanese Patent No. 51/039625; and Japanese Patent No. 80/045067. While the production of betaine from sugar beet molasses is a known commercially feasible process as described in the above listed patents, it is not known to produce betaine from stillage. This is because of a serious fouling of the chromatographic resin by yeast cells, microorganisms and other compounds. The manufacture of glycerol, betaine, succinic acid and free flowing distiller's dry grain, or the production of both betaine and glycerol from beet molasses stillage, by processes such as those to be described hereinafter has not, insofar as is known to the present inventor, been described in any prior patent or publication other than that which has resulted from the aforementioned priority application.
For the first time, it is now possible to recover betaine and/or glycerine from stillage of ethanol fermentations with sugar beet derivatives. The preparation of the feed with microfiltration and the two chromatographic separation steps for the production of pure glycerine and betaine are critical. Cross-flow microfiltration with inorganic membranes followed by enzymatic hydrolysis of proteinaceous matter and/or removal of potassium sulfate crystals in the permeate (if required) will yield a truly clarified stillage. The clarified stillage may now be concentrated to a very high solids concentration for further processing in two chromatographic separation steps, each with its own specific resin, yielding high purity glycerine and betaine streams. This novel process has several advantages over existing and different methods in use as described in the patents listed above, such as energy and water savings, reduced capitol investment, very high solids concentrations, high quality glycerine and betaine.
The processes and apparatus of the present invention contemplate the production of each or all or any combination of the products mentioned in a commercially feasible manner in a fermentation and distillation or similar process.